Not applicable.
Not Applicable.
1. Field of the Invention
The invention relates generally to medical devices and procedures. More particularly, this invention relates to a knotless bioabsorbable suture anchor system for attaching soft tissue to bone, and to methods for attaching soft tissue to bone.
2. Background of the Invention
Soft tissues, such as ligaments, tendons and muscles, are attached to a large portion of the human skeleton. In particular, many ligaments and tendons are attached to the bones which form joints, such as shoulder and knee joints. A variety of injuries and conditions require attachment or reattachment of a soft tissue to bone. For example, when otherwise healthy tissue has been torn away from a bone, surgery is often required to reattach the tissue to the bone to allow healing and a natural reattachment to occur.
A number of devices and methods have been developed to attach soft tissue to bone. These include screws, staples, cement, suture anchors, and sutures alone. Some of the more successful methods involve the use of a suture anchor to attach a suture to the bone, and tying the suture in a manner that holds the tissue in close proximity to the bone.
The tissue may be attached to the bone during open surgery, or during closed (e.g., arthroscopic) surgical procedures. Closed surgical procedures are preferred since they are less invasive and are less likely to cause patient trauma. In a closed surgical procedure, the surgeon performs diagnostic and therapeutic procedures at the surgical site through small incisions, called portals, using instruments specially designed for this purpose. One problem encountered in the less invasive, closed surgical procedures is that the surgeon has significantly less room to perform the required manipulations at the surgical site. Thus, devices and methods are needed which will allow a surgeon to effectively and easily attach tissue to bone in the small spaces provided by less invasive surgical procedures.
Conventional methods for attaching soft tissue to bone typically require that the surgeon tie a knot in the suture thread to attach the suture to an anchor, or to attach the tissue to the bone using the suture. Knot tying at the surgical site in closed surgical procedures, and even in open surgery, is difficult and time consuming due to inherent space constraints. Further, knots and other bulky attachment means can irritate tissue over time.
Knotless suture anchor systems have been developed for use with closed surgical procedures, and U.S. Pat. No. 5,569,306 provides one example of such a system. Although generally useful, such systems can be limited to use only with certain types or shapes of tissue, or to use with certain anatomical structures. Proper attachment of soft tissue requires that it be placed in the anatomically correct position to promote optimal healing.
A further knotless suture anchor system is disclosed in U.S. Pat. No. 5,782,864. While useful, the suture anchor and system disclosed in this patent is not believed to be absorbable. That is, the suture anchor is made of a metal, which will remain permanently implanted in the patient.
Further, some conventional knotless suture anchor systems may require, in order to attach a broader array of tissue shapes to bone, that the suture anchor pass though the tissue to be attached. This is undesirable because it unnecessarily irritates the injured tissue and it requires opening a much larger hole in the tissue.
There is thus a need for an improved system for anchoring soft tissue to bone which reduces or eliminates the need to tie suture knots at the surgical site. Further, there is a need for an improved system for anchoring soft tissue to bone which is fast and easy to deploy. It would also be advantageous to provide at least a partially absorbable knotless suture anchor and system so as to encourage natural regrowth of the damaged or torn tissue.
The present invention provides a knotless suture system for anchoring tissue to bone. The system includes a suture anchor configured to radially expand into bone. The suture anchor has a proximal end and a distal end with a bore formed therein. The system further includes a first loop of suture thread attached to the distal end of the suture anchor, a suture needle, and a second loop of suture thread attached to the needle and interlocked with the first loop of suture thread. The system also includes an expander pin that is configured and sized for insertion into the bore of the suture anchor, causing the anchor to radially expand from a first outer diameter to a second outer diameter. A method is also provided by which a detached tissue may be securely attached to bone in an anatomically correct position without the need to tie a knot.
In one embodiment, the system includes a suture anchor having proximal and distal ends, wherein a suture-engaging tip is present at the distal end and a separate, radially expandable sleeve, having a bore formed longitudinally therethrough, forms a proximal end of the suture anchor. The tip and the sleeve are mated to one another, such as by a threaded engagement. The system further includes an expander pin for insertion into the bore of the expandable sleeve. In this embodiment, the expandable sleeve may include two substantially flat, opposed sides between the proximal and distal ends and separated by the bore. As noted above, the system includes a first loop of suture thread attached to the tip, a second loop of suture thread interlocked with the first loop, and a suture needle having a first, tissue penetrating end and a second, trailing end attached to the second loop. In one embodiment, the expander pin is made from a bioabsorbable material.
In another embodiment, the system comprises a suture anchor which includes a unitary base member having a distal end and a proximal end with a bore formed longitudinally therein, and a separate expander pin for insertion into the bore of the base member to effect radial expansion of at least a portion of the base member. The distal end of the base member has a suture thread-engaging groove for seating a portion of the first loop of suture thread. Additionally, the base member can have two substantially flat, opposed sides between the distal and proximal ends to allow suture thread to easily pass around the base member. The flat sides can each contain a longitudinally oriented slit, which may be matable with the protrusions on opposite sides of the expander pin. Preferably, the base member and expander pin are formed from a bioabsorbable material.
In an embodiment that is particularly useful in closed surgery, the second suture loop is formed using a suture loop closure and is attached to a hollow suture needle by means of a slot provided in a wall of the hollow needle. This embodiment may also employ an actuator, disposed within the hollow needle, which can be selectively deployed to disengage the second suture loop from the needle. The hollow needle used with this embodiment preferably is part of an elongate tool, such as a suture inserter, that is useful in closed surgical procedures. The hollow needle typically forms the distal end of such a tool.
Various types of inserter tools are also included with the system of the invention. The inserter tool generally includes an elongate shaft element, and a pusher or actuation element may be slidably mounted on the shaft Actuation of the pusher causes the expander pin to be disposed within the bore of the radially expandable sleeve or proximal component of the anchor to effect radial expansion.
The system may be used in a method wherein the suture needle and the attached second suture loop are passed through a detached segment of tissue. The second suture loop is pulled through the detached tissue until a portion of the interlocked first suture loop extends through the detached tissue. The suture anchor is then maneuvered so that a portion of the first suture loop is seated within a suture-engaging groove at the distal end of the suture anchor. The anchor is then inserted into a predrilled bore in a portion of bone. Once the suture anchor is inside the bone, the expander pin is driven into the bore of the suture anchor, expanding the base radially to the extent that external walls of the suture anchor engage bone. The suture anchor is stabilized in a friction fit within the bore, and the detached tissue is thereby attached to the bone in the desired position.
The term xe2x80x9csuture needlexe2x80x9d is used herein to encompass both conventional suture needles, used in open surgical procedures, as well as suture needles that may form a hollow, distal end of an elongate tool useful with closed surgical procedures.